Originally Posted by

**bramp** Hello,

I'm a PhD student and I'm a little embarrassed to be asking for Maths help on here, but there is something I couldn't find out by googling, so I figured I'll ask here.

I have been running two sets of experiments, the first is a base line, and the second is hopefully an improvement on the first. I repeat each experiment many times and get a set of values, for example:

first = ( 2, 3, 3, 2, 4, 2 ) mean = 2.67, stddev = 0.82, 95% interval = +/- 0.65

second = (4, 5, 6, 5, 4, 5 ) mean = 4.83, stddev = 0.75, 95% interval = +/- 0.6

Now I can work out a 95% confidence interval for both sets of values. In my report I've been writing that the first experiment on average is 2.67 +/- 0.65, and the second is 4.83 +/- 0.6. Thus the second experiment produces values 1.81 (4.83/2.67) higher (and better) than the first experiment. However I do not know what the confidence intervals would be on this (1.81) value.

I had thought I could divide the intervals together for example the first min value divided by the second's min value. But I have a feeling this isn't right.

Hopefully this has explained my problem, and that someone is able to help.

Thanks

Andrew

P.S These are not the real values from my experiment and some I just made up, but I hopefully want to work out the confidence intervals for both discrete and continuous data.